On windows NT systems there is no central system log but if you using UNIX system and if you got the message “Central system log cannot be read” then check the following info…
If you got the following message on you SM21 transaction code

Then you can simply try to following way ;

– Shutdown the SAP system

– Delete / Rename the SLOG file from the operating system level

- Start the SAP system

and now you can try the tcode SM21 again , if problem still exist then you can check the related oss note 25526